Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 134,916	$ 168,517
Marketable securities	108,535	228,962
Prepaid expenses and other current assets	4,892	5,100
Total current assets	248,343	402,579
Property and equipment, net	1,893	1,388
Restricted cash	849	564
Total assets	251,085	404,531
Current liabilities:
Accounts payable	13,030	12,817
Accrued expenses	36,807	22,352
Total current liabilities	49,837	35,169
Other liabilities	1,196	845
Total liabilities	51,033	36,014
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized at September 30, 2017 and December 31, 2016; no shares issued or outstanding at September 30, 2017 and December 31, 2016
Common stock, $0.0001 par value per share; 120,000,000 shares authorized at September 30, 2017 and December 31, 2016; 37,524,984 and 37,222,518 shares issued at September 30, 2017 and December 31, 2016, respectively; 37,524,638 and 37,222,172 shares outstanding at September 30, 2017 and December 31, 2016, respectively	4	4
Treasury stock, at cost, 346 shares at September 30, 2017 and December 31, 2016	(17)	(17)
Additional paid-in capital	721,105	688,959
Accumulated deficit	(521,025)	(320,327)
Accumulated other comprehensive loss	(15)	(102)
Total stockholders’ equity	200,052	368,517
Total liabilities and stockholders’ equity	$ 251,085	$ 404,531